66 ASSIMILATION OF HYDROGEN. 



an organic compound is supplied to a plant by the 

 decomposition of water. The process of assimila- 

 tion, in its most simple form, consists in the 

 extraction of hydrogen from water, and carbon from 

 carbonic acid, in consequence of which, either all 

 the oxygen of the water and carbonic acid is sepa- 

 rated, as in the formation of caoutchouc, the 

 volatile oils which contain no oxygen, and other 

 similar substances, or only a part of it is exhaled. 



The known composition of -the organic com- 

 pounds most generally present in vegetables, 

 enables us to state in definite proportions the 

 quantity of oxygen separated during their formation. 



36 eq. carbonic acid and 22 eq. hydrogen derived ) _ ^ , 

 from 22 eq. water . . .3 



with the separation of 72 eq. oxygen. 



36 eq. carbonic acid and 36 eq. hydrogen derived ? 



from 36 eq. water . . 3 



with the separation of 72 eq. oxygen. 



36 eq. carbonic acid and 30 eq. hydrogen derived > Starch 



from 30 eq. water . . .3 



with the separation of 72 eq. oxygen. 



36 eq. carbonic acid and 16 eq. hydrogen derived > j, . 



from 16 eq. water . . 3 ~~ 



with the separation of 64 eq. oxygen. 



36 eq. carbonic acid and ,18 eq. hydrogen derived ) Tartaric Acid 



from 18 eq. water . . 5 ~~ 



with the separation of 45 eq. oxygen. 



36 eq. carbonic acid and 18 eq. hydrogen derived > Malic Acid 



from 18 eq. water . . .3 



with the separation of 54 eq. oxygen. 



36 eq. carbonic acid and 24 eq. hydrogen derived > =O il of Turpentine 

 from 24 eq. water . . .3 



with the separation of 84 eq. oxygen. 



It will readily be perceived that the formation of 



